ary = [[1, 6, 7], [1, 4, 9], [1, 8, 3]]

ary2 = ary.sort_by { |a, b, c| b:odd? ? b : c }

arr2 = ary.sort_by { |a, b, c| a.odd? ? a : b.odd? ? b : c }

ary2 = ary.sort_by do |a, b, c|
  if a.odd?
    a
  elsif b.odd?
    b
  else
    c
  end
end